1. Field of the Invention
The present invention relates generally to a Broadband Wireless Access (BWA) system, and, in particular, to an apparatus and method for transmitting a service guide in a BWA system, the service guide including a mapping table of application layer name tags versus Internet Protocol (IP) layer name tags or Medium Access Control (MAC) layer name tags with respect to broadcast channels, a table of broadcasting information, authentication information, an actual broadcast channel name mapped to an application layer name tag, and a combination thereof.
2. Description of the Related Art
As generally known in the art, communication systems have been primarily developed for voice communication services, but they are also evolving to provide data services and various multimedia services. However, conventional communication systems, which are mainly directed to providing voice communication services, still have a narrow data transmission bandwidth and require a high subscription fee. For these reasons, they cannot satisfy diversified user demands. Furthermore, in line with rapid development in the communication industry and ever-increasing demands on Internet services, it is important to provide communication systems capable of providing Internet services efficiently. As a result of these trends, BWA systems having a bandwidth large enough to both satisfy the increasing user demands and provide efficient Internet services have been proposed.
In addition to providing voice communication services, BWA systems aim at supporting a variety of low-speed and high-speed data services and multimedia application services (e.g., high-quality moving pictures) in combination. Based on wireless media using a broadband of 2 GHz, 5 GHz, 26 GHz, or 60 GHz, BWA systems are able to access a Public Switched Telephone Network (PSTN), Public Switched Data Network (PSDN), Internet network, International Mobile Telecommunications-2000 (IMT-2000) network, and Asynchronous Transfer Mode (ATM) network in a mobile or stationary environment. In other words, BWA systems can support a channel transmission rate of at least 2 Mbps. BWA systems may be classified into broadband wireless local loops, broadband mobile access networks, and high-speed wireless Local Area Networks (LANs) according to the terminal's mobility (stationary or mobile), communication environment (indoor or outdoor), and channel transmission rate.
The standardization of wireless access schemes of BWA systems such as WiMAX is being conducted by Institute of Electrical and Electronics Engineers (IEEE), which is one of the international standardization organizations, particularly by the IEEE 802.16 standardization group. Compared to conventional wireless communication systems for voice communication services, IEEE 802.16 communication systems have a larger data transmission bandwidth. Therefore, they can transmit more data for a limited period of time and share all user channels (or resources) for efficient channel utilization. Also, since Quality of Service (QoS) features are guaranteed, users can be provided with various services of different qualities, depending on the service characteristics.
The IEEE 802.16 system supports the standard of a MultiCast and BroadCast Service (referred to as MCBCS or MBS depending on the intentions of operators or standardization groups). In the MCBCS standard, an MBS (Multicast and Broadcast Service) zone is a zone including one or more subcells that transmit the same broadcast channel at the same frequency at the same time. The subcells in the MBS zone use the same Connection IDentifier (CID) for the same broadcast channel or content. Herein, the subcell is a group having one frequency and one sector. In general, a Multicast CID (MCIDs) has a 1:1 mapping relationship with a broadcast channel that has a broadcast channel IP, and a Logical Channel ID (LCID) has a 1:1 mapping relationship with a content ID that is used to discern between broadcast contents included in the payload of the same broadcast channel IP. A base station (BS) transmits an MBS zone ID list through a Downlink Channel Descriptor (DCD) message to broadcast information about whether it can support an MCBCS service and information about whether it belongs to an MBS zone. The MBS zone may include one or more base stations.
In the MCBCS service, unlike a conventional unicast service, a plurality of base stations transmit the same broadcast contents at the same frequency at the same time and a receiving (RX) terminal combines packets received from the base stations, thereby increasing the RX performance. For the conventional unicast service, when a user terminal is located at a cell edge, transmission/reception of data is not smooth due to a large inter-cell interference. However, for the MCBCS service, because neighbor BSs transmit the same contents at the synchronized time, the user terminal can receive and combine the same data from a plurality of base stations even when a user terminal is located at a cell edge. This is called a macro diversity gain.
The MCBCS-related standard defined in the IEEE 802.16e has the following limitations. The standard does not provide a broadcast message indicating to which MCID each broadcast channel IP is mapped. Therefore, each user terminal needs to generate a unicast flow at every process of handoff, broadcast channel request (selection), deletion or change and accordingly the user terminal must maintain an awake state. Thus, a restriction is imposed on the maximum number of awake-state user terminals per sector. This promises that a unicast flow occurs frequently even for a user terminal receiving only a broadcast service. Therefore, the system must allocate a Channel Quality Information CHannel (CQICH) for such a case. Herein, the MCID is a factor that is used at a MAC layer to discriminate between broadcast channel data bursts and discriminate between MBS_DATA_IEs in an MBS-MAP message.
Also, when a handoff condition occurs in the awake or sleep state, even a user terminal receiving only a broadcast service performs a handoff process, which leads to a waste of air resources and system processing capacity. Herein, the broadcast reception may be interrupted when the handoff fails.
Also, air resources are wasted due to performance of a broadcast channel process operation on each user terminal. When each user terminal performs the request/change/deletion process for all the broadcast channels, a MAP overhead increases and also a data burst of a signaling MAC message is wasted.
Also, there is an increased delay due to each broadcast channel process operation. That is, a delay increases because a user terminal performs each broadcast channel process operation through a Base Station (BS), an ASN-GW, an MCBCS server, and a policy server. In particular, the user terminal is susceptible to a channel change time, and a channel change causes a large transmission latency of several hundreds of ms (milliseconds) because it requires both of the deletion and request processes.
Also, when each user terminal performs the broadcast channel request/deletion/change process, an uplink subframe is essentially needed, power is wasted due to uplink transmission, and a macro diversity scheme is further complicated.
Also, a performance degradation, an increased signaling overhead, and many abnormal cases are generated when entities for allocation of MBS zones, MCIDs or LCIDs, generation/transmission of broadcast tables of Service Providers (SPs), and generation/management of MBS-MAP messages, which are important, are determined unsuitably.